Basic operations of MySQL views (5)_MySQL

use zhaojd_test;  //选择一个自己创建的库
create table t_product( //创建表
  id int primary key,
  pname varchar(20),
  price decimal(8,2)
); 
insert into t_product values(1,'apple',6.5); //向表中插入数据
insert into t_product values(2,'orange',3); //向表中插入数据
create view view_product as select id,name from t_product; //创建视图
select * from view_product;

mysql> create view view_test1 as select 3.1415926;
Query OK, 0 rows affected (0.07 sec)
mysql> select * from view_test1;
+-----------+
| 3.1415926 |
+-----------+
| 3.1415926 |
+-----------+
1 row in set (0.00 sec)

CREATE TABLE t_group(
  id INT PRIMARY KEY AUTO_INCREMENT,
  NAME VARCHAR(20)
);
CREATE TABLE t_student(
  id INT PRIMARY KEY AUTO_INCREMENT,
  NAME VARCHAR(20),
  sex CHAR(1),
  group_id INT,
  FOREIGN KEY (group_id) REFERENCES t_group (id)
);
//t_group表中插入数据
INSERT INTO t_group (NAME) VALUES('group_1');
INSERT INTO t_group (NAME) VALUES('group_2');
INSERT INTO t_group (NAME) VALUES('group_3');
INSERT INTO t_group (NAME) VALUES('group_4');
INSERT INTO t_group (NAME) VALUES('group_5');
//t_student表中插入数据
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_1','M',1);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_2','M',1);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_3','M',2);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_4','W',2);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_5','W',2);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_6','W',2);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_7','M',3);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_8','W',4);
INSERT INTO t_student (NAME,sex,group_id) VALUES('zjd_9','W',4);
================================================================
mysql> create view view_test2 as select count(name) from t_student;
Query OK, 0 rows affected (0.71 sec)
mysql> select * from view_test2;
+-------------+
| count(name) |
+-------------+
|      9 |
+-------------+
1 row in set (0.01 sec)

mysql> create view view_test3 as select name from t_student order by id desc;
Query OK, 0 rows affected (0.06 sec)
mysql> select * from view_test3;
+-------+
| name |
+-------+
| zjd_9 |
| zjd_8 |
| zjd_7 |
| zjd_6 |
| zjd_5 |
| zjd_4 |
| zjd_3 |
| zjd_2 |
| zjd_1 |
+-------+
9 rows in set (0.00 sec)

mysql> create view view_test5 as select s.name from t_student s,t_group g where s.group_id=g.id and g.id=2;
Query OK, 0 rows affected (0.07 sec)
mysql> select * from view_test5;
+-------+
| name |
+-------+
| zjd_3 |
| zjd_4 |
| zjd_5 |
| zjd_6 |
+-------+
4 rows in set (0.00 sec)

mysql> create view view_test6 as select s.name from t_student s left join t_group g on s.group_id=g.id where g.id=2;
Query OK, 0 rows affected (0.09 sec)
mysql> select * from view_test6;
+-------+
| name |
+-------+
| zjd_3 |
| zjd_4 |
| zjd_5 |
| zjd_6 |
+-------+
4 rows in set (0.01 sec)

mysql> create view view_test7 as select s.name from t_student s where s.id in(select id from t_group);
Query OK, 0 rows affected (0.08 sec)
mysql> select * from view_test7;
+-------+
| name |
+-------+
| zjd_1 |
| zjd_2 |
| zjd_3 |
| zjd_4 |
| zjd_5 |
+-------+
5 rows in set (0.00 sec)

mysql> create view view_test8 as select id,name from t_student union all select id,name from t_group;
Query OK, 0 rows affected (0.08 sec)
mysql> select * from view_test8;
+----+---------+
| id | name  |
+----+---------+
| 1 | zjd_1  |
| 2 | zjd_2  |
| 3 | zjd_3  |
| 4 | zjd_4  |
| 5 | zjd_5  |
| 6 | zjd_6  |
| 7 | zjd_7  |
| 8 | zjd_8  |
| 9 | zjd_9  |
| 1 | group_1 |
| 2 | group_2 |
| 3 | group_3 |
| 4 | group_4 |
| 5 | group_5 |
+----+---------+
14 rows in set (0.01 sec)

mysql> show tables;
+------------------+
| Tables_in_zhaojd |
+------------------+
| t_group     |
| t_product    |
| t_student    |
| v_product    |
| view_test1    |
| view_test2    |
| view_test3    |
| view_test4    |
| view_test5    |
| view_test6    |
| view_test8    |
+------------------+
11 rows in set (0.00 sec)

mysql> show table status from zhaojd \G
*************************** 1. row ***************************
      Name: t_group
     Engine: InnoDB
    Version: 10
   Row_format: Compact
      Rows: 5
 Avg_row_length: 3276
  Data_length: 16384
Max_data_length: 0
  Index_length: 0
   Data_free: 7340032
 Auto_increment: 6
  Create_time: 2016-08-19 16:26:06
  Update_time: NULL
   Check_time: NULL
   Collation: utf8_general_ci
    Checksum: NULL
 Create_options:
    Comment:
============================================================= 
      Name: view_test8
     Engine: NULL
    Version: NULL
   Row_format: NULL
      Rows: NULL
 Avg_row_length: NULL
  Data_length: NULL
Max_data_length: NULL
  Index_length: NULL
   Data_free: NULL
 Auto_increment: NULL
  Create_time: NULL
  Update_time: NULL
   Check_time: NULL
   Collation: NULL
    Checksum: NULL
 Create_options: NULL
    Comment: VIEW

 mysql> show create view view_test8 \G
*************************** 1. row ***************************
View: view_test8
Create View: CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `view_test8` AS select `t_student`.`id` AS `id`,
`t_student`.`NAME` AS `name` from `t_student` union all select `t_group`.`id` AS `id`,`t_group`.`NAME` AS `name` from `t_group`
character_set_client: utf8
collation_connection: utf8_general_ci
1 row in set (0.00 sec)
//根据执行结果可以发现，SHOW CREATE VIEW语句返回两个字段，分别为表示视图名的View字段和关于视图定义的Create view字段。

mysql> desc view_test8;
+-------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id  | int(11)   | NO  |   | 0    |    |
| name | varchar(20) | YES |   | NULL  |    |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.02 sec) 

mysql> use information_schema;
Database changed
mysql> select * from views where table_name='view_test8' \G
*************************** 1. row ***************************
    TABLE_CATALOG: def
    TABLE_SCHEMA: zhaojd
     TABLE_NAME: view_test8
   VIEW_DEFINITION: select `zhaojd`.`t_student`.`id`AS`id`,`zhaojd`.`t_student`.`NAME` AS `name` from `zhaojd`.`t_student` union all select `zhaojd`.`t_group`.`id` AS`id`,`zhaojd`.`t_group`.`NAME` AS `name` from `zhaojd`.`t_group`
    CHECK_OPTION: NONE
    IS_UPDATABLE: NO
       DEFINER: root@localhost
    SECURITY_TYPE: DEFINER
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
1 row in set (0.01 sec)

mysql> use zhaojd;
Database changed
mysql> show tables;
+------------------+
| Tables_in_zhaojd |
+------------------+
| t_group     |
| t_product    |
| t_student    |
| v_product    |
| view_test1    |
| view_test2    |
| view_test3    |
| view_test4    |
| view_test5    |
| view_test6    |
| view_test8    |
+------------------+
11 rows in set (0.00 sec)
mysql> drop view view_test1, view_test2;
Query OK, 0 rows affected (0.01 sec)
mysql> show tables;
+------------------+
| Tables_in_zhaojd |
+------------------+
| t_group     |
| t_product    |
| t_student    |
| v_product    |
| view_test3    |
| view_test4    |
| view_test5    |
| view_test6    |
| view_test8    |
+------------------+
9 rows in set (0.00 sec)

DROP VIEW view_name; 
CREATE VIEW view_name as 查询语句;